What if you could support a third-party agenda while also voting for a Democrat or Republican?

Voters in New York can, and often do. It's called electoral fusion, and it used to be commonplace across the country.

And if a Democratic Philadelphia state representative and an allied third party are successful, it would become legal once again in Pennsylvania, potentially helping boost third parties' profile and shaping the agendas of the two major parties.

"In a one-party town, how do you really express yourself in a meaningful and nuanced way?" said State Rep. Chris Rabb, the Democrat who in 2016 was elected to represent part of Northwest Philadelphia, including Mount Airy and Chestnut Hill.

But Rabb was also nominated by the progressive Working Families Party, and the Department of State blocked it. State law forbids electoral fusion, among other restrictions on third parties.

Rabb and the Working Families Party sued, saying the ban violates their constitutional rights by preventing parties from nominating the candidates they choose. Now, two years later, the Pennsylvania Supreme Court is poised to release a decision: Is the state ban on electoral fusion constitutional?

What electoral fusion is and what it could change

The practice is fairly straightforward: Multiple parties can nominate the same candidate and list the person on their "lines" on the ballot. All votes for that candidate are combined when determining the winner.

It was done regularly before most states banned it at the end of the 19th century. Teddy Roosevelt won Pennsylvania's votes in the 1912 presidential election, for example, on a three-way ticket of the Bull Moose, Washington, and Roosevelt Progressive Parties. (Woodrow Wilson, a Democrat, won the election, defeating Roosevelt and ousting Republican President William Howard Taft.)

Today, fusion is legal in only a handful of states, and even then is often not used. One notable exception is New York, where minor parties can play an influential role.

Proponents say fusion allows voters to support a third-party agenda without "spoiling" the election or "wasting" votes, since they can vote for a major-party candidate while casting a ballot for a third-party platform.

"It would be another way to let people know what you stood for ideologically," said Robin Kolodny, a Temple University political science professor who has written about electoral fusion and third parties.

The minor parties also gain some negotiating power, Kolodny said, because Democrats and Republicans will want their nominations. They can thus influence Democratic and Republican platforms.

"Of course you want to be able to recruit your own people and do those kinds of things," but sometimes other parties' candidates are good matches, said Brandon Evans, head of Pennsylvania's Working Families Party. "In terms of taking someone else's person, we're saying, 'Actually, that person is our kind of person, reflects our kind of values.'"

Why Rabb and the Working Families Party sued

Rabb, a longtime Philadelphia Democratic committee person who portrays himself as anti-establishment, beat a machine-backed candidate in the 2016 primary.

Shortly after, he said, the Working Families Party approached him to be its nominee.

"I kind of scratched my head and said, 'Well, the Democrats kind of took care of that,'" Rabb said, laughing. He eventually said yes, and the WFP filed papers to nominate him, only to have the Department of State reject the attempt.

The party asked Rabb whether he'd join a lawsuit.

"I said, 'You're kidding me, right? You're really trying to get me in trouble,'" Rabb said. "I just beat the establishment candidate and now you want me to sue the state that I'm going to be working for in the state legislature."

The law, they argue, violates the Pennsylvania Constitution's guarantee that "elections shall be free and equal" and its protections for free speech and association.

"The party is denied its right to nominate the candidate of its choice, the candidate that best reflects its values, and the candidate that can provide it a pathway to power," said Jordan B. Yeager, the attorney representing the plaintiffs. "And it means the party's voters are likewise prevented from expressing themselves fully at the ballot box."

How the state is defending the anti-fusion laws

The state Attorney General's Office, which is handling the defense of the case, deferred response to the Department of State, which declined to comment.

Unlike in other states where fusion means the candidate would appear on the ballot multiple times, the current system in Pennsylvania simply places multiple party labels next to the candidate's name, e.g. "Christopher M. Rabb (Democratic Party/Working Families Party.)"

Because the state uses election results to classify political organizations into different levels — political party, minor political party, and political body — with different requirements for placing a candidate on the ballot, fusion would disrupt the system.

"Permitting the Working Families Party to cross-nominate Rabb as its candidate, and allowing his candidacy to be the determinant of whether the Working Families Party qualifies as a 'political party' for the next election cycle, would permit the Working Families Party to leverage Democratic Party support to benefit itself," the state wrote in a brief before the state Supreme Court.

The Department of State also warns of a hypothetical situation where Democrats or Republicans could falsely circulate petitions to nominate a candidate of their choice under the third party's name.

"Election officials accept the first valid set of nomination papers bearing the name of any particular political organization, and reject any others filed later," they wrote.

The Working Families Party is willing to forgo the vote count for political party categorization, he said, and the state could also move to a ballot system where the candidate would be listed multiple times with different parties, the way other states do.

In the case of the state's hypothetical concern that major parties would interfere with the minor parties, Yeager dismissed it as paternalistic.

"There's no evidence that that's an actual problem," he said. "And if we're going to deny constitutional rights, we shouldn't do it based on unsubstantiated fears."

What comes next

The case was appealed to the Pennsylvania Supreme Court after the state won in Commonwealth Court. The court heard oral argument in September and could rule at any time.

If it upholds the Commonwealth Court decision, the ban on electoral fusion will stand.